后台查找页面上所有的TextBox控件

foreach (Control txtobj in this.Page.Controls)  
  {  
      if (txtobj.GetType().Name == "TextBox")  
      {  
          //((TextBox)txtobj).Text = "";   
          TextBox tb = new TextBox();  
          tb = (TextBox)this.FindControl(txtobj.ID);  
          tb.Text = "";  
      }  
  }